[ThinLTO] Revert part of r289843 that belonged to another patch.
[ThinLTO] Revert part of r289843 that belonged to another patch.

The code change for D27687 accidentally got committed along with the
main change in r289843. Revert it temporarily, so that I can recommit it
along with its test as intended.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@289875 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm